Tom
We primarily use 940's to transfer data through TCC. As to their future viability, ultimately none of them will be able to be an internet access point but as to when that happens depends on which wireless carrier you are using (if you are already using one). 940's were made to a specific carrier so they couldn't have been switched from say Verizon to AT&T or vice versa, also both carriers suspended activation of 3G devices in 2018 (Verizon was 06/01, AT&T was 12/31) so if you aren't using cell service it's unlikely that a modem will be able to be activated. For devices that are currently active if you're using the Verizon network (like we are) then cell service for it will continue until 12/31/19 at which time Verizon is retiring it's 3G network and you'll need to go to hotspot or replace it with a 941. If you're using the AT&T network you should have cell service until what's currently being predicted as no sooner than 12/31/21. though AT&T hasn't announced a hard retirement date they have suggested they won't be repairing any down 3G towers.
Remember this effects TSC3's as well so if your using cell service with them you're essentially going to WIFI at some point in the next 3 years.